The Kingdom of Africa was a North African kingdom which existed from 1146 to 1160, with Tripoli serving as its capital. King Roger II of Sicily made his first African conquest in 1123 when he captured the island of Pantelleria, and, in 1135 - with the help of Sicilian Arabs - he captured the pirate den on the island of Djerba. Roger was motivated both by the protection of key trade routes and by his goal of building a vast Mediterranean Christian empire, with the former Roman province of Africa Proconsularis serving as his starting point. In 1142, after the city of Mahdia was unable to pay for Sicilian grain, Roger forced Mahdia to become a protectorate. In 1146, Roger besieged and captured Tripoli, which had suffered from several famines and was in the throes of a civil war. In 1148, Sousse and Sfax fell. Sicilian rule was maintained by military garrisons placed in the major towns, and the Sicilians protected the North African Christians and minted their own coins. Roger encouraged Muslim refugees in Sicily to re-settle in Africa, and Norman Africa became rich and prosperous (unlike the rest of North Africa), with Sicilian grain preventing Norman Africa from suffering from the same famines which plagued the rest of North Africa, and Tripoli becoming repopulated due to its prosperity and trade with Sicily and Genoa. The local Muslims were made to pay the same religious tax which they had previously levied onto the Jews and Christians of the region, and the Christian community - largely consisting of servants and slaves - benefited from Norman rule. From 1158 to 1160, the Almohad Caliphate reconquered Africa from King William I of Sicily, and, in 1180, the Sicilians and Almohads made peace, abandoning North Africa.